The Carboxy-Terminal Region of Flavobacterium johnsoniae SprB Facilitates Its Secretion by the Type IX Secretion System and Propulsion by the Gliding Motility Machinery
The Carboxy-Terminal Region of Flavobacterium johnsoniae SprB Facilitates Its Secretion by the Type IX Secretion System and Propulsion by the Gliding Motility Machinery
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DOI：
10.1128/jb.00218-19
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发表时间：
2019-10-01
影响因子：
3.2
通讯作者：
McBride, Mark J.
中科院分区：
文献类型：
--
作者：
Kulkarni, Surashree S.;Johnston, Joseph J.;McBride, Mark J.
约氏黄杆菌SprB沿着细胞表面快速移动，导致滑动运动。SprB的分泌需要IX型分泌系统（T9 SS）。由T9 SS分泌的蛋白质通常具有属于A型CTD或B型CTD家族的保守C末端结构域（CTD）。将70至100个氨基酸的A型CTD附着到外源蛋白上允许其分泌。B型CTD很常见，但很少受到关注。分析融合至跨越SprB型B CTD的区域的外源蛋白超级折叠绿色荧光蛋白（sfGFP）（sfGFP-CTDSprB）的分泌。218个氨基酸或更长的CTD导致sfGFP的分泌，而149个氨基酸的区域则不会。一些sfGFP以可溶性形式分泌，而其余的附着在细胞表面上。表面附着的sfGFP沿着细胞被快速地沿着推进，表明与运动机制的生产性相互作用。这并没有导致快速的细胞运动，这显然需要额外的SprB区域。sfGFP-CTDSprB的分泌需要与位于sprB下游的sprF共表达。SprF在序列上与牙龈卟啉单胞菌PorP相似。大多数F.编码具有B型CTD的蛋白质的约翰逊氏菌基因位于porP/sprF样基因的紧邻上游。将sfGFP与来自一种这样的蛋白质（Fjoh_3952）的B型CTD融合。这导致sfGFP仅在与其同源PorP/SprF样蛋白共表达时分泌。这些结果强调了需要B型CTD的延伸区域和与适当的PorP/SprF样蛋白共表达以有效分泌和货物蛋白的细胞表面定位。约翰逊氏菌滑动运动粘附素SprB通过IX型分泌系统（T9 SS）递送至细胞表面，并通过运动机制沿细胞快速沿着推进。这种6，497个氨基酸的蛋白质如何与分泌和运动机器相互作用尚不清楚。SprB的C-末端218个氨基酸与外源货物蛋白的融合导致其分泌，附着于细胞表面，并通过运动机制快速运动。SprB的有效分泌需要与外膜蛋白SprF共表达。在C-末端区域与SprB具有序列相似性的分泌蛋白在拟杆菌门中是常见的，并且可能在粘附、运动和毒力中起作用。
Flavobacterium johnsoniae SprB moves rapidly along the cell surface, resulting in gliding motility. SprB secretion requires the type IX secretion system (T9SS). Proteins secreted by the T9SS typically have conserved C-terminal domains (CTDs) belonging to the type A CTD or type B CTD family. Attachment of 70- to 100-amino-acid type A CTDs to a foreign protein allows its secretion. Type B CTDs are common but have received little attention. Secretion of the foreign protein super-folder green fluorescent protein (sfGFP) fused to regions spanning the SprB type B CTD (sfGFP-CTDSprB) was analyzed. CTDs of 218 amino acids or longer resulted in secretion of sfGFP, whereas a 149-amino-acid region did not. Some sfGFP was secreted in soluble form, whereas the rest was attached on the cell surface. Surface-attached sfGFP was rapidly propelled along the cell, suggesting productive interaction with the motility machinery. This did not result in rapid cell movement, which apparently requires additional regions of SprB. Secretion of sfGFP-CTDSprB required coexpression with sprF, which lies downstream of sprB. SprF is similar in sequence to Porphyromonas gingivalis PorP. Most F. johnsoniae genes encoding proteins with type B CTDs lie immediately upstream of porP/sprF-like genes. sfGFP was fused to the type B CTD from one such protein (Fjoh_3952). This resulted in secretion of sfGFP only when it was coexpressed with its cognate PorP/SprF-like protein. These results highlight the need for extended regions of type B CTDs and for coexpression with the appropriate PorP/SprF-like protein for efficient secretion and cell surface localization of cargo proteins.IMPORTANCE The F. johnsoniae gliding motility adhesin SprB is delivered to the cell surface by the type IX secretion system (T9SS) and is rapidly propelled along the cell by the motility machinery. How this 6,497-amino-acid protein interacts with the secretion and motility machines is not known. Fusion of the C-terminal 218 amino acids of SprB to a foreign cargo protein resulted in its secretion, attachment to the cell surface, and rapid movement by the motility machinery. Efficient secretion of SprB required coexpression with the outer membrane protein SprF. Secreted proteins that have sequence similarity to SprB in their C-terminal regions are common in the phylum Bacteroidetes and may have roles in adhesion, motility, and virulence.